MANILA, Philippines — The US military said it had launched a search and resecue operation after reports a marine may have fallen overboard from an American warship as it sailed through Philippine waters.

The US 13th Marine Expeditionary Unit said a member, who was not named, may have gone overboard Thursday morning.

The 13th MEU is conducting search & rescue operations for one of our Marines. We are conducting an extensive search w/ support from all available agencies & we will continue until every option has been exhausted. The most updated info will be posted here when available. pic.twitter.com/zpkpDYeisM

Aircraft on board the USS Essex are searching waters off the Sulu Sea and the Surigao Strait while multiple searches are also being made inside the ship itself, the unit said on its social media sites late Friday.

The ship was conducting "routine operations in the Sulu Sea" at the time, the California based unit said.

"All of our sailors, marines and available assets aboard the USS Essex have been and will continue to be involved in this incredibly important search and rescue operation," added the search commander, US Navy Captain Gerald Olin.

The Philippine coastguard are also taking part in what is now an expanded search covering about 3,000 square nautical miles (10,290 square kilometres), it added.

Sulu Sea, the Philippines' largest inland waterway, sprawls over the central and southern sections of the Asian archipelago, a US military ally.